linux-kernel - Re: [PATCH 3/4] Drivers: hv: vmbus: Add hooks for per-CPU IRQ

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Date:   Tue, 27 Nov 2018 07:20:56 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     KY Srinivasan <kys@...rosoft.com>,
        "will.deacon@....com" <will.deacon@....com>,
        "catalin.marinas@...m.com" <catalin.marinas@...m.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        vkuznets <vkuznets@...hat.com>
Subject: Re: [PATCH 3/4] Drivers: hv: vmbus: Add hooks for per-CPU IRQ

On Mon, Nov 26, 2018 at 08:56:50PM +0000, Michael Kelley wrote:
> From: Greg KH <gregkh@...uxfoundation.org>  Monday, November 26, 2018 11:57 AM
> 
> > > > You created "null" hooks that do nothing, for no one in this patch
> > > > series, why?
> > > >
> > >
> > > hv_enable_vmbus_irq() and hv_disable_vmbus_irq() have non-null
> > > implementations in the ARM64 code in patch 2 of this series.  The
> > > implementations are in the new file arch/arm64/hyperv/mshyperv.c.
> > > Or am I misunderstanding your point?
> > 
> > So you use a hook in an earlier patch and then add it in a later one?
> > 
> > Shouldn't you do it the other way around?  As it is, the earlier patch
> > should not work properly, right?
> 
> The earlier patch implements the hook on the ARM64 side but it is
> unused -- it's not called.  The later patch then calls it.  Wouldn't the
> other way around be backwards?

Ah, it wasn't obvious that the previous patch added it at all, why not
just make that addition part of this patch?

> The general approach is for patches 1 and 2 of the series to provide
> all the new code under arch/arm64 to enable Hyper-V.  But the code
> won't get called (or even built) with just these two patches because
> CONFIG_HYPERV can't be selected.  Patch 3 is separate because it
> applies to architecture independent code and arch/x86 code -- I thought
> there might be value in keeping the ARM64 and x86 patches distinct. 
> Patch 4 applies to architecture independent code, and enables the
> ARM64 code in patches 1 and 2 to be compiled and run when
> CONFIG_HYPERV is selected.
> 
> If combining some of the patches in the series is a better approach, I'm
> good with that.

Ok, that makes more sense, if it is easier to get the ARM people to
review this, that's fine.  Doesn't seem like anyone did that yet :(

sorry for the noise,

greg k-h